I did some tri tips using a bag of oak wood chunks I lit in the chimney and burned to coals. You'd need a lot of that to fire a 6 -12 hour cook though.
briquettes and lump are all made from wood. there will always be a slightly smokey flavor when using either for fuel vs gas. that's why most folks prefer the taste of charcoal to gas. my most recent cook http://www.bbq-brethren.com/forum/showthread.php?t=171776 was done using the walmart backyard grill briquettes(which are just rebranded RO briqs) and no smoke wood. everything still had a decent smokey taste.